Storm Forecast
Valid: Sat 20 Feb 2016 06:00 to Sun 21 Feb 2016 06:00 UTC
Issued: Fri 19 Feb 2016 22:26
Forecaster: TASZAREK

A level 1 was issued for N Greece mainly for the severe wind gusts.

SYNOPSIS

A trough E of Iceland with a well pronounced cold sector moves eastwardly and provides a dynamic airflow over British Isles. A belt of ridge (1025 hPa) extends from Azores to CNTRL Mediterranean inhibiting convective activity. A cold drop located SE of Spain moves northwardly and provides conditions for the development of DMC mainly on the marine areas. In the end of the forecast period the cold drop breaks the ridge over Spain and France. A passage of the long wave with a separating cold drop is forecast over Adriatic, Balkan Peninsula and Aegean Sea. A main jet stream stretches from N Atlantic through North Sea, Central Europe, Balkan Peninsula and E Mediterranean.

DISCUSSION

... Greece, Aegean Sea...

Within the passage of a long wave and later on a cold drop, an overlap of thermodynamic instability, strong QG lift (left exit of the jet, advection of PVU) and a vertical wind shear (DLS 20-30 m/s) will take place over N Greece. Although a boundary layer's moisture will be not impressive (mixing ratio 5-6 g/kg) a steepening lapse rates will result in a CAPE up to 200-400 J/kg over the land surface. A limiting factor for the severe weather threat is an uncertain position of the jet. In current GFS output the jet hooks an instability areas over N Greece, and therefore a few isolated severe wind gust events within the supercells cannot be not ruled out. If the jet will be placed further south, convection will not benefit from vertical wind shear and thus severe weather will be unlikely. After the convective cells will move over Aegean Sea, thermodynamic instability will increase and also the lightning potential. However, in current understanding, the jet will move further south and a severe weather potential will drop. Thunderstorms should go on until the end of the forecast period and reach Dodecanese during the nighttime hours.